How is it possible for radio waves to travel at the speed of light? After all, sound and music come out of our radios, and most of us learned in school that light travels faster than sound. Well, radio waves travel at the speed of light because they are not sound waves. We’ll unpack this more below.
What Are Radio Waves?
Radio waves are the building block of radio communication. Radio waves are technically electromagnetic radiation and have the longest wavelengths in the electromagnetic spectrum. Although you cannot see them, radio waves have the same properties as light, such as:
- standing waves
Electromagnetic waves travel at the speed of light in a vacuum, while sound waves cannot travel through a vacuum. According to modern physics, light is the fastest thing in the universe, traveling at 186,282 miles per second in a vacuum.
When traveling through material, the speed of radio waves is affected by the medium’s permittivity and permeability. Outside the vacuum, the air in the Earth’s atmosphere is thin enough that radio waves still travel at speeds close to the speed of light.
How Do Radios Work?
If radio waves aren’t sound waves, then how do radios produce sound? Radios must have both transmitters and receivers to function. Transmitters, antennas, and receivers allow energy to be generated, sent out into space, and received miles away.
- Transmitters artificially generate radio waves as charged particles undergo acceleration.
- Using an antenna, the radio receiver can intercept and receive the radio waves that the transmitter emits.
- The receiver converts the electromagnetic waves to mechanical vibrations in the speaker, which creates the sound waves we enjoy.
What Objects Produce Radio Waves?
In outer space, objects that have a changing magnetic field produce radio waves. Almost all astronomical objects emit radio radiation, but some of the most potent sources include:
- certain nebulas
- radio galaxies
Radio telescopes are more prominent than optical telescopes and measure radio waves from space to help astronomers learn about objects’ composition, motion, and structure in space.
Many household objects use radio frequency communication here on Earth, such as radios, cell phones, baby monitors, and wireless networks.
Are Radio Waves the Same Thing as Radiation?
Electromagnetic radiation is energy that travels through space and objects. It’s moving energy. The significant difference between high-powered gamma-rays from nuclear bombs and our TVs and microwaves is how much energy the waves have. Technically, they are all electromagnetic radiation, but the waves have different wavelengths, energy, and frequency, creating a different effect.
On the electromagnetic spectrum, radio waves have the lowest frequency or energy. On the other hand, microwaves have a higher frequency, and infrared rays and x-rays have an even higher frequency than that.
What Is Radio Frequency (RF)?
As we’ve discussed so far, radio waves are energy. As radio waves are emitted, they create a pattern of mountains and valleys that look like the waves of an ocean. The complete wave pattern is a cycle, which repeats. How many times it repeats per second is called frequency, measured in hertz (Hz) units. So the Hz unit refers to the number of cycles per second.
- A kilohertz (kHz) is 1 thousand hertz
- A megahertz (MHz) is 1 million hertz
- A gigahertz (GHz) is 1 billion hertz
Radio frequency (RF) is the oscillation rate of an electromagnetic field or mechanical system from 3 kHz to 300 GHz. These frequencies produce energy that is released as radio waves and used in communication devices. Devices that utilize radio frequencies include
- mobile phones
- carrier current systems: telephony and control circuits
What Are the Different Types of Radio Waves?
Within the broader electromagnetic (EM) spectrum, we have the radio frequency (RF) spectrum. The radio waves we are talking about have the lowest frequencies and longest wavelengths.
The radio spectrum is not infinite. National departments such as the British Broadcasting Corp (BBC) and the US Department of Commerce National Telecommunications and Information Administration manage users and the frequency allocations.
Here are the nine bands of the radio spectrum with their frequency and wavelength ranges.
- Extremely Low Frequency (ELF): <3 kHz; >100km
- Very Low Frequency (VLF) 3-30 kHz; 10 to 100 km
- Low Frequency (LF) 30-300 kHz; 1 m to 10 km
- Medium Frequency (MF) 300 kHz to 3MHz 100 m to 1km
- High Frequency (HF) 3 to 30 MHz; 10 to 100 m
- Very High Frequency (VHF) 30 to 300 MHz; 1 to 10m
- Ultra High Frequency (UHF) 300 MHz to 3 GHz; 10 cm to 1m
- Super High Frequency (SHF) 3 to 30GHz; 1 to 1 cm
- Extremely High Frequency (EHF) 30 to 300 GHz; 1 mm to 1 cm
Marine and aviation radio use low to medium frequency radio bands. These waves have a long-range and can penetrate water and rock. Low to medium frequencies also transmit commercial AM (amplitude modulation) radio, which falls between 535 kHz and 1.7 MHz.
Higher frequency radio bands include HV, VHF, and UHF. In addition, these bands include FM (frequency modulation) radio, public service radio, broadcast television sound, mobile phones, and Global Positioning System (GPS).
Shortwave radio falls in the HF band, falling within the shortwave spectrum of 1.7 MHz to 30 MHz.
The highest frequencies of SHF and EHF are limited in range but often used for short-range, high-bandwidth communication between fixed locations. SHF is also for Wi-Fi and Bluetooth.
Who Discovered Radio Waves?
Scottish mathematician James Clerk Maxwell first predicted electromagnetic waves in 1865. His electromagnetism theories are now known as Maxwell’s equations. Later, German physicist Heinrich Hertz conducted lab experiments that generated the first radio wave and proved Maxwell’s theories. The Hertz unit for measuring frequency is named after him.
Guglielmo Marconi, an Italian inventor and electrical engineer, invented the first radio transmitters and receivers. In 1909, Marconi won the Nobel Prize in physics for his work in radio transmission.
Do Radio Waves Travel at the Speed of Light? Conclusion
Yes, radio waves indeed travel at the speed of light. Although radio waves ultimately come through our speakers as sound, they are electromagnetic radiation with properties similar to light.